Reproduction
The wood mouse has a breeding season from February to October in which multiple matings occur between males and females resulting in scramble competition. Such behavioral characteristics result in sperm competition and multiple paternity litters. The society is polygynous with copulation resulting from scramble competition during reproductive periods. Males possess a sac known as the cauda epididymus which stores sperm and lies underneath the scrotum protrusion. Temperature regulation ensures maximum sperm output.
One interesting observation about the species, in particular the males, is the morphology of the spermatozoa. They develop falciform (sickle shaped) heads after meiosis and before spermiation (release during ejaculation). The hook located at the tip of the head adheres to the surface of the head prior to deployment. Propidium iodide staining revealed that only the basal surface of the hook is of nuclear origin. These apical hooks are deployed in female reproductive tract (mechanism responsible involved the remodeling of actin filaments in the hook). Deployed apical hooks combine with apical hooks and flagella of other spermatozoa. The aggregates of spermatozoa that result form "mobile trains", which have experimentally been determined to possess better motility in the female reproductive tract. The mobility of these mobile trains was also found to be influenced by premature acrosome reactions, altruistic acts performed by some spermatozoa for the benefit of other genetically similar gametocytes. This altruism follows a "green beard" mechanism in which spermatozoa discern the genetic similarity of surrounding gametocytes (such mechanisms are rare because they must code for a recognizable phenotype as well as response mechanisms). Once spermatozoa of similar genotypes are identified, altruism genes are turned on to elicit a response that seeks to conserve the genes present in the other cell, even if it results in the destruction of the cell performing the action.
The gestation period of wood mice is of 25–26 days and each female produces on average five young. The offspring become independent after about three weeks and become sexually active after two months.
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Famous quotes containing the word reproduction:
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